JPS6337605A - High-frequency magnetic field generating and detecting apparatus - Google Patents

Abstract

PURPOSE:To obtain a stable high-frequency magnetic field generating and detecting apparatus having high efficiency by unbalanced-feeding a section between the connecting end of a second variable capacitor and a transmission line and a high-frequency grounding point as the connecting midpoint of a first fixed capacitor and a second fixed capacitor and resonating a microwave circuit. CONSTITUTION:A section between the connecting-end hot side with a transmission line 10 of a second variable capacitor 9b and a high-frequency grounding point for a microwave circuit is unbalanced-fed. Since the grounding side of an input/output terminal 6 is connected electrically to a conductor cylinder 12 and the potential of the conductor cylinder 12 is brought to ground potential, load can be supplied with maximum power when a coaxial cable having unbalanced impedance and a high-frequency transmitter-receiver are coupled with the input/output terminal 6, and power detected is maximized. Since voltage having equal magnitude and reverse polarity is applied to electrodes 7a and 7b at that time, an LC series resonance circuit is balanced-fed completely. It is because the connecting midpoint of a first fixed capacitor 8a and a second fixed capacitor 8b represents a high-frequency grounding point E.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a high frequency magnetic field generator/detector, particularly to a high frequency magnetic field generator/detector used in a magnetic resonance apparatus.

[Conventional technology]

Figure 3 shows, for example, [Journal of Magnetics]
Resonance (Journalor MagneticR
esonande) J, Vol. 36, pp. 447-4
51 (1979) 1 is a perspective view showing a conventional high-frequency magnetic field generator/detector, and in the figure (1)
are a pair of H-shaped conductor plates, such as copper plates, which are arranged to constitute a hollow cylindrical body, such as a hollow cylindrical coil body. These conductor plates (1) are vertical
It has a non-protruding part (1a) called a vertical band and a protruding part (1b) called a wing. (2) is a fixed capacitor inserted between adjacent protrusions (1b) of the conductor plate (1). (3) is a pair of conductor rings for electric field shielding installed inside the protrusion (1b) via an insulating layer (not shown), one conductor ring (3a) is a top fist guard.
The other conductor ring (3b) is called the bottom guard ring. (41L) + (4b) are a first electrode and a second electrode formed integrally with the conductor plate (1) and the conductor ring (6), respectively. (5a) and (5b) are a first variable capacitor and a second variable capacitor, respectively, for impedance matching, which are connected in series between the first electrode (4a) and the second electrode (4b). (6) is a high frequency input/output terminal connected to a high frequency transmitter/receiver (not shown), and is connected to the first electrode (5a) via the first variable capacitor (5a).
4a) and directly connected to the second electrode (4b).

A conventional high-frequency magnetic field generator/detector is configured as described above, and the conductor plate (1), fixed capacitor (2), and conductor ring (3) form a three-dimensional circuit that equivalently functions as an LC series resonant circuit. Furthermore, a first electrode (4a), a second electrode (
4b) are capacitively coupled, the resonance frequency can be adjusted by adding the first variable capacitor (5a) and the second variable capacitor (5b). Therefore, the first variable capacitor (5a), the second variable capacitor (
5b), the input/output terminal (6) can be connected to a transmitter/receiver having a predetermined impedance. Note that the conductor ring (6) is used for electric field shielding as described above, that is, for reducing dielectric loss within the measurement object due to the generated electric field when the measurement object is installed in the high-frequency magnetic field generation Φ detector.

[Problems to be Solved by the Invention] Conventional high-frequency magnetic field generators and detectors do not take into account the balanced/unbalanced transformation of circuit impedance, so the outer conductor of the coaxial line connected to the input/output terminal (6) There were problems such as a surface current flowing through the surface and making the operation unstable, resulting in low efficiency. Specifically, there have been various problems such as radiation loss from the coaxial line or incorporation of external noise, and depending on the state of the coaxial line, current leakage to the ground.

This invention was made to solve these problems, and aims to provide a stable and efficient high-frequency magnetic field generator/detector.

[Means for solving problems]

The high frequency magnetic field generator/detector according to the present invention includes a first fixed capacitor and a second fixed capacitor that are connected in series between at least one set of protrusions and have a connection midpoint and an equal capacitance.
a fixed capacitor, and a first fixed capacitor connected in parallel with the first fixed capacitor and the second fixed capacitor connected in series.
a variable capacitor, a second variable capacitor connected to one end of this first variable capacitor, a transmission line connected to the other end of this second variable capacitor, and a ground side of this transmission line connected to the connection midpoint. A conductive wire to be connected, an input/output terminal connected to the other end of the transmission line, and a conductor tube installed outside the conductor plate concentrically with the conductor plate, and at least one of the transmission line and the input/output terminal. One ground side is electrically connected to the conductor cylinder.

[For production]

In this invention, the three-dimensional circuit is made to resonate by supplying unbalanced power between the connection end of the second variable capacitor and the transmission line and the high frequency ground point which is the connection midpoint of the first fixed capacitor and the second fixed capacitor. This makes it more stable and efficient.

〔Example〕

FIG. 1 is a perspective view showing an embodiment of the present invention.
) to (3) are exactly the same as those in conventional high-frequency magnetic field generators and detectors. (7L), (7'F)) are electrodes formed integrally with a pair of protrusions (1b) of the conductor plate (1). (8a) and (8b) are a first fixed capacitor and a second fixed capacitor, respectively, having the same capacitance C1, and are connected in series between electrodes (7a) and (7b).

(9a) is a first variable capacitor for the LC series resonant circuit and for impedance matching, and the first fixed capacitor (8a) and second fixed capacitor (8b) are connected in series.
) are connected in parallel. (9b) is a second variable capacitor for impedance conversion, which is connected to one end of the first variable capacitor (9a).
) constitutes an unbalanced impedance matching circuit (9). (10) is a transmission line, such as a coaxial line, connected between the other end of the second variable capacitor (9b) and the input/output terminal (6). (11) is the ground side of this transmission line (10) [The hot side is the second variable capacitor (9b
) is the connection end. ], the first fixed capacitor (8a
) and the second fixed capacitor (8b) at the connection midpoint E (hereinafter referred to as
This is called the high frequency ground point. ). (
12) is the above-mentioned elements (1) to (3) and (6) to (
The conductor cylinder (12) houses the high-frequency magnetic field generator/detector of the present invention consisting of 11), for example, a conductor (metallic) cylinder, and the ground side of the input/output terminal (6) is attached to the conductor cylinder (12) with screws, pressure welding, crimp bonding, or Electrically connected by soldering. Further, the conductor cylinder (12) may be a cylinder made of an insulator with metal foil pasted on the inner or outer wall.

The angle formed by the non-protruding portion (1a) of the conductor plate (1) is
70° x θ<100°, preferably 75° x θ<90°
It is.

The high frequency magnetic field generation system of the present invention configured as described above.
In the detector, the first variable capacitor (9a) adjusts the resonance frequency and impedance matching frequency of the three-dimensional circuit that operates as an equivalent series resonant circuit. In addition to this, the second variable capacitor (9b) converts the impedance to a predetermined value, for example 50Ω. At this time, unbalanced power is fed between the connection end (hot side) of the second variable capacitor (9b) with the transmission line (10) and the high frequency ground point of the seven-dimensional circuit. Furthermore, the ground side of the input/output terminal (6) is electrically connected to the conductor cylinder (12) to connect the conductor cylinder (12) to the conductor cylinder (12).
By setting the potential of 12) to ground potential, when a coaxial cable with unbalanced impedance and a high frequency transmitter/receiver are connected to the input/output terminal (6), the maximum power can be supplied to the load, and the detected power can also be reduced. Maximum. In this case, voltages of equal magnitude and opposite polarity are applied to the electrodes (7a) and (7b), so that as a result, the LC series resonant circuit is completely balanced. This is the first
Fixed capacitor (8a) and second fixed capacitor (8b)
This is because the midpoint of the connection is the high frequency ground point E. This is the reason why the stability and efficiency of the high-frequency magnetic field generator/detector can be increased. Note that HM is the generated high-frequency magnetic field, and the arrow indicates the direction of the magnetic field, that is, the direction perpendicular to the plane of the window formed by the non-protruding portion (1a) and the protruding portion (1b).

Further, two or more pairs of conductor plates (1) can be used, and two or more pairs of conductor plates (1) can be used.
A modification of FIG. 1 using a pair of conductor plates (1) is shown in a perspective view in FIG. In this case, the input/output terminal (6a).

When power is supplied to (6b) with a phase difference of 90°, a rotating magnetic field can be generated.

Furthermore, in the above-described embodiments, the hollow cylindrical body is used as a hollow cylindrical body, but the hollow cylindrical body may be a hollow elliptical body.

Especially when measuring the human body's chest, abdomen, etc.
It is preferable to use a hollow elliptical body that conforms to the shape of the human body. In this case, the longitudinal axis direction may be parallel to or perpendicular to the direction of the generated high-frequency magnetic field. Furthermore, in the embodiment shown in Fig. 1, the ground side of the input/output terminal and the conductor cylinder are connected, but it is also possible to electrically connect a part of the external conductor of the transmission line to the conductor cylinder by, for example, pressure welding, crimping, or soldering. Also good.

〔Effect of the invention〕

As explained above, the present invention provides a first fixed capacitor and a second fixed capacitor that are connected in series between at least one set of protrusions and have a connection midpoint and equal capacitance, and a second fixed capacitor that is connected in series. A first variable capacitor connected in parallel with the first fixed capacitor and the second fixed capacitor, a second variable capacitor connected to one end of the first variable capacitor, and a transmission line connected to the other end of the second variable capacitor. , a conductor connecting the ground side of this transmission line to the connection midpoint, an input/output terminal connected to the other end of the transmission line, and a conductor tube installed outside the conductor plate concentrically with the conductor plate. Since the ground side of at least one of the transmission line and the input/output terminal is electrically connected to the conductor cylinder, there is an effect that a stable and efficient high frequency magnetic field generator/detector can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an embodiment of the present invention, FIG. 2 is a perspective view showing a modified example, and FIG. 3 is a perspective view showing a conventional high frequency magnetic field generator/detector. In the figure, (1) is a conductive plate, (1a) is a non-protruding part, (
1b) is a protrusion, (2) is a fixed capacitor, (3) is a conductor ring, (6) is an input/output terminal, (8a) is a first fixed capacitor, (8b) is a second fixed capacitor, (9) is a Impedance matching circuit, (9a) is the first variable capacitor, (
9b) is the second variable capacitor, (1 is the transmission line, (
11) is a conducting wire, (12) is a conductor tube, and (El is a high frequency ground point. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (12)

[Claims] (1) At least one pair of conductor plates arranged to form a hollow cylindrical coil body that is H-shaped, a fixed capacitor that capacitively couples the protrusions of these conductor plates, and the protrusion. a three-dimensional circuit consisting of a conductor ring installed concentrically with the conductor plate inside the conductor plate and functioning equivalently as an LC series resonant circuit; A first fixed capacitor and a second fixed capacitor having capacitance, a first variable capacitor connected in parallel with the first fixed capacitor and the second fixed capacitor connected in series, and a first variable capacitor connected to one end of the first variable capacitor. a second variable capacitor, a transmission line connected to the other end of the second variable capacitor, a conductor connecting the ground side of the transmission line to the connection midpoint, and a conductor connected to the other end of the transmission line. An input/output terminal, and a conductor tube installed outside the conductor plate concentrically with the conductor plate, and a ground side of at least one of the transmission line and the input/output terminal is electrically connected to the conductor tube. , a high frequency magnetic field generator/detector, characterized in that unbalanced power is supplied between the other end of the second variable capacitor and the connection midpoint. (2) The high-frequency magnetic field generator/detector according to claim 1, wherein the hollow cylindrical body is a hollow cylindrical body. (3) The high frequency magnetic field generator/detector according to claim 1, wherein the hollow cylindrical body is a hollow ellipsoidal body. (4) The high-frequency magnetic field generation/detector according to claim 3, wherein the direction of the generated high-frequency magnetic field is the direction of the major axis of the ellipse of the hollow elliptical body. (5) The high-frequency magnetic field generator/detector according to claim 3, wherein the direction of the short axis of the ellipse of the hollow elliptical body is the direction of the generated high-frequency magnetic field. (6) The high frequency magnetic field generator/detector according to any one of claims 1 to 5, wherein the conductor cylinder is fitted with a metal cylinder. (7) Claim 1, characterized in that the conductor tube is a cylinder made of an insulator with metal foil pasted on the wall surface.
The high frequency magnetic field generator/detector according to any one of Items 1 to 5. (8) The high-frequency magnetic field generator/detector according to claim 7, characterized in that a metal foil is attached to the inner wall of the cylinder. (9) The high-frequency magnetic field generator/detector according to claim 7, characterized in that a metal foil is attached to the outer wall of the cylinder. (10) The high frequency magnetic field generator/detector according to any one of claims 1 to 9, wherein the transmission line is a coaxial line. (11) The high frequency magnetic field generator/detector according to any one of claims 1 to 10, characterized in that the ground side of the transmission line is directly connected to the conductor tube by pressure welding, crimping, or soldering. (12) The high-frequency magnetic field generator/detector according to any one of claims 1 to 10, characterized in that the ground side of the input/output terminal is directly connected to the conductor tube by screw pressure welding, crimping, or soldering. .